Fundamentals Of HVAC Control Systems

Transcription

ASHRAE Hong Kong Chapter Technical WorkshopFundamentals of HVACControl Systems18, 19, 25, 26 April 2007 2007 ASHRAE Hong Kong ChapterSlide 1

Chapter 5Control Diagramsand Sequences 2007 ASHRAE Hong Kong ChapterSlide 2

Design Criteria - IThe control system: Must meet the needs of the process Should control the process as directly aspossible Must be designed to work with the HVACsystem and vice versa 2007 ASHRAE Hong Kong ChapterSlide 3

Design Criteria - IIThe control system: Should minimize energy consumptionwhile meeting process goals Must meet the budget Must be designed for maximum simplicity Must be easy to understand and maintain 2007 ASHRAE Hong Kong ChapterSlide 4

Aims of HVAC Control SystemLower energy costLower operations costIncrease flexibility 2007 ASHRAE Hong Kong ChapterEnsure quality buildingenvironmentSlide 5

Key Personnel HVAC system designer Installation of mechanical partsElectrical contractor Provide advice on control products & featuresMechanical contractor Responsible for conceptual design, tendering, etc.Controls vendor sales representative Design, etc.Installation of electrical partsInstallationControls contractor Details of control system part of the installation 2007 ASHRAE Hong Kong ChapterSlide 6

Typical Installation Tasks Mechanical contractor Installation of control valves, dampers, air and watermeasuring devicesProvision of control dampersInstallation of duct mounted smoke detectorsProvision of variable speed drivesProvision of starters for package equipment and specialmachinery (e.g. chiller)Provision of starters with thermal overload protection ormotors with integral thermal overload protection 2007 ASHRAE Hong Kong ChapterSlide 7

Typical Installation Tasks Electrical contractor (the controls work) Motor starters Fire alarm and life safety control relays and switchesand all smoke detectors Wiring and mounting line voltage controls Power to control panels Controls contractor Selection of control valves Selection of actuators for both valves and dampers Control and interlock wiring 2007 ASHRAE Hong Kong ChapterSlide 8

Control Diagrams and Symbols Symbols for HVAC system components Refer to ASHRAE Fundamentals Handbook 2005 Chp.37, Abbreviations and Symbols Refer to other local standards or guidelines Usually specified in the contract drawings & documents Generic control diagrams Using generic symbols to describe and define therequirements of the control systemShop drawings by contractorsSpecific hardware control diagrams 2007 ASHRAE Hong Kong ChapterSlide 9

[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 10

Generic Symbols - I 2007 ASHRAE Hong Kong ChapterSlide 11

Generic Symbols - II 2007 ASHRAE Hong Kong ChapterSlide 12

Writing Control Sequences - I Break the sequence into logical partsClearly indicate the control point andcontrolled device and how the setpoint isdeterminedConsider using enabling interlocksState the required/desired setpointsEach variable should be controlled by asingle control loop 2007 ASHRAE Hong Kong ChapterSlide 13

Writing Control Sequences - II State how each device should be controlledwhen the system operates normally, shutsdown and in emergenciesSpecify the normal position of importantcontrolled devicesControl sequences should be as specific aspossibleSimplify control sequences to avoid bugs 2007 ASHRAE Hong Kong ChapterSlide 14

Single-Zone Air Handler 2007 ASHRAE Hong Kong ChapterSlide 15

Single-Zone Unit WithDual Setpoint Thermostat 2007 ASHRAE Hong Kong ChapterSlide 16

Typical VAV System 2007 ASHRAE Hong Kong ChapterSlide 17

Control diagram of a VAV reheat system for year-round operation[Source: Wang, S. K., 2001. Handbook of Air Conditioning and Refrigeration] 2007 ASHRAE Hong Kong ChapterSlide 18

Pressure Independent Control 2007 ASHRAE Hong Kong ChapterSlide 19

Chilled Water, Economizer and HotWater Sequencing 2007 ASHRAE Hong Kong ChapterSlide 20

Reset Schedule(16 deg C)(13 deg C)F(13 deg C) 2007 ASHRAE Hong Kong ChapterF(18 deg C)Slide 21

Discharge air control loop with reset[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 22

[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 23

Thermostat model of proportional control with deadbandand dual throttling range 2007 ASHRAE Hong Kong ChapterSlide 24

Practical Examples forAir Handling System 2007 ASHRAE Hong Kong ChapterSlide 25

Practical Examples forAir Handling System Reference document: Honeywell, 1997. Engineering Manual of AutomaticControl for Commercial Buildings - Heating, Ventilating,Air Conditioning, SI Edition., Honeywell, Inc.,Minneapolis, MN, pp. 201-260.Air Handling System Control Applications Abbreviations and symbolsRequirements for Effective Control (general guidelines)Different HVAC processesASHRAE Psychrometric Charts 2007 ASHRAE Hong Kong ChapterSlide 26

Practical Examples forAir Handling System Typical format and design information Functional description (w/ diagram)FeaturesConditions for successful operationLimitationsSpecificationsPsychrometric aspects 2007 ASHRAE Hong Kong ChapterSlide 27

Fan system start-stop control[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 28

Fixed quantity of outdoor air controlReturn airDeliver/supply airTwo-positiondamper[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 29

Mixed air control[Source: Honeywell, 1997. Engineering Manual ofAutomatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 30

Economizer cycle control (outdoor air dry bulb)[Source: Honeywell, 1997. Engineering Manual ofAutomatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 31

Economizer cycle control (outdoor air enthalpy)[Source: Honeywell, 1997. Engineering Manual ofAutomatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 32

Economizer cycle control (outdoor air enthalpy)[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 33

Economizer cycle control (outdoor air/return air enthalpy comparison)[Source: Honeywell, 1997. Engineering Manual ofAutomatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 34

Mixed air control with economizer cycle[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 35

Mixed air control with economizer cycle[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 36

Economizer cycle control of space temperature withsupply air temperature setpoint reset[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 37

Designing Direct Digital Control(DDC) Systems 2007 ASHRAE Hong Kong ChapterSlide 38

Design DDC systems Design an effective DDC system Simplicity & effective technical communicationTypes of DDC signals Digital output (DO), e.g. command to open a valveDigital input (DI), e.g. status signal from a fanAnalogue input (AI), e.g. room temperature Analogue output (AO), e.g. command to modulate acontrol valve 2007 ASHRAE Hong Kong ChapterSlide 39

A simple DDC control system[Source: Shadpour, F., 2001. The Fundamentals of HVAC Direct Digital Control] 2007 ASHRAE Hong Kong ChapterSlide 40

Componentsof a energymanagementsystem (EMS)with directdigital control(DDC) 2007 ASHRAE Hong Kong ChapterSlide 41

ManagementlevelCentral station communicationvia gatewaysOperational levelControl levelField levelCentral stationOutstation, discrete controllerSensor, switch, etc.Levels of control in building energy management system 2007 ASHRAE Hong Kong ChapterSlide 42

Example of system architecture for building management system 2007 ASHRAE Hong Kong ChapterSlide 43

Six steps of DDC system design System schematicControl point designationsPoint listDDC system architectureSequence of operationSpecifications 2007 ASHRAE Hong Kong ChapterSlide 44

System schematic for a constant volume single zone AHU[Source: Shadpour, F., 2001. The Fundamentals of HVAC Direct Digital Control] 2007 ASHRAE Hong Kong ChapterSlide 45

Control point designations for a constant volume single zone AHU[Source: Shadpour, F., 2001. The Fundamentals of HVAC Direct Digital Control] 2007 ASHRAE Hong Kong ChapterSlide 46

[Source: Shadpour, F., 2001. The Fundamentals of HVAC Direct Digital Control] 2007 ASHRAE Hong Kong ChapterSlide 47

An example of DDC system architecture[Source: Shadpour, F., 2001. The Fundamentals of HVAC Direct Digital Control] 2007 ASHRAE Hong Kong ChapterSlide 48

OperatorInterfaceWorkstationWebServerPrimary BusPrimary ControlUnitPrimary ControlUnitSecondary BusSecondary BusAir HandlerControllerLightingControllerCentral ceVAVBoxSystem architecture of building automation system 2007 ASHRAE Hong Kong ChapterSlide 49

[Source: Shadpour, F., 2001. The Fundamentals of HVAC Direct Digital Control] 2007 ASHRAE Hong Kong ChapterSlide 50

Show on drawingsIndicate in specificationsLocation of devicesQuality of componentsSize of componentsMaterial requiredQuantity of componentsWorkmanship[Source: Shadpour, F., 2001. The Fundamentals of HVAC Direct Digital Control] 2007 ASHRAE Hong Kong ChapterSlide 51

Useful References Books: Honeywell, 1997. Engineering Manual of AutomaticControl for Commercial Buildings - Heating, Ventilating,Air Conditioning, SI Edition., Honeywell, Inc.,Minneapolis, MN.à 77-1200.pdf Shadpour, F., 2001. The Fundamentals of HVAC DirectDigital Control: Practical Applications and Design, 2nded., Hacienda Blue, Escondido, CA. 2007 ASHRAE Hong Kong ChapterSlide 52

Useful References Research papers: Hui, S. C. M., 2007. Latest trends in building automationand control systems, In Proc. of the CAI Symposium2007 on Intelligent Facility Management and IntelligentTransport, 28 March 2007, Hong Kong, 10 pages.à http://web.hku.hk/ cmhui/CAI-2007 SamHui.pdf Spitzer, D. W., 2002. Selecting flow measurementdevices, HPAC Engineering, 74 (12): 52-59. Website: DDC Online [www.ddc-online.org] 2007 ASHRAE Hong Kong ChapterSlide 53

Controls vendor sales representative Provide advice on control products & features Mechanical contractor Installation of mechanical parts Electrical contractor Installation of electrical parts Controls contractor Details of control system part of the installation Installation Design, etc.